Hi Thomas & all others - a cup would do not 4kg! I suppose I could go to the beach and get some for free. When you did the water volume test on Silimax did you dry the sand? using an oven? With a very close pack as I expect SM is, it will have air in it, this releases when wet and the bulk decreases.
I see this at the beach with our fine white sand if you place it in a bucket and add water it debulks...
I'll re-phrase my stance on grading: I don't see a leap forward in modulus from the grading. The technical docs don't support this, some of the tests in threads here don't support this, my tests don't support it and the more I look the less confidence I have about it. I want a number I can design with and I want a simple repeatable production process. The people that go deep into grading (diy machine builders) and do it don't test so don't know what they have. Many are grading to reduce cost not increase modulus. The civil engs are interested in compressive modulus so they can build taller buildings that don't buckle and only test in compression. Its a difficult area. So you have quartz which is 70GPa modulus even if its 100% efficient at 80% volume fraction its 56GPa which it isn't. So at 50% strain efficiency its 56/2=28GPa which it could/should be. I can build fibreglass (FG) laminates at 30-32GPa, tension, compression and flexure any day I want plus its 500MPa strength plus. Been testing laminates at this for years. If I build in FG I can machine it, if I build in concrete I can't unless I use inserts or diamond tooling. I want a material that gives and does everything! and the current answer is laminated aluminium.... E=70GPa damp, light, machinable, easy to make, can be bent, laser cut etc etc.... If I use local CSA grout I'll use 35GPa but I'll check this out in Plank3 maybe... tomorrow morn I release Plank2.... as I know the vol fraction I can check the maths. If attractive or close then I'll consider grading to improve the modulus but if it has poor modulus vs its volume fraction then there's no point, its the end of the road for that idea.... laminated aluminium is the clearest best defined direction at the moment. Thanks for participating appreciate all commentary appreciated... Peter
I'm reviewing the build costs on Brevis-HD/YaG /Scoot at the moment and I'm having some of the parts requoted in 3mm gal steel, 5mm aluminium and laminated versions of these vs thick stainless steel. Will be an interesting costing exercise...